Takafumi Saikawa
Takafumi Saikawa
rebased
TODO: 1. create a renaming PR : finite_preimage -> finite_inj_preimage 2. redo this PR
can you suggest a better name?
turned into a draft until I figure out how to handle mc master
PR #14327 is weakly related to this one (touching the same function).
I suggest keeping 4 lemmas as is, and additionally, provide a unified interface lemma that use the constant_sign predicate
that notion seems to deserve a definition and a notation. what about generalizing it a bit as "continuous within X and derivable in the interior of X" for any set...
(though derivability needs more structure than just topology, so it will not actually be "any" topological space. manifolds?)
> fyi @t6s the former looks internal to contra, thus not meant to be exported, while the latter looks like a misnomer since it is about double negations
> fyi @t6s the former looks internal to contra, thus meant to be exported, while the latter looks like a misnomer since it is about double negations